CAP patient characteristics. Smokers: S. pneumo, H. influenzae, MoraxellaPost viral bronchitis: S. pneumoNo co-morbidity: atypicals, viralAlcoholic: S. pneumo, anaerobesIV drug user: S. aureusEpidemic: Legionnaire'sAirway obstruction: anaerobesAnimals: Psittacosis, Tularemia, Coxiella burneti
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1. Community acquired pneumonia and treatment options
6 mechanisms in pathogenesis of pneumonia – (inhalation, aspiration, direct inoculation, reactivation, defects in pulmonary defenses, blunted cellular or humoral immune response)
In general, clinical presentation: pleuritic chest pain, fever, cough, decreased breath sounds, dull to percussion, egophony
Classified as “typical” or “atypical” or viral
Typical = S. pneumoniae, H. influenza, S. aureus, enteric gram negative bacteria. More segmental or lobar infiltrate.
Atypical = Mycoplasma, Legionella, Chlamydia pneumonia. More diffuse infiltrate. Sputum gram stain usually negative.
Empiric treatment prior to susceptibility testing- cover S. pneumoniae, S. aureus, H. influenzae. Give amoxicillin-clavulanate, and 2nd or 3rd generation cephalosporin, or respiratory fluoroquinolone (3rd and 4th generation).
2. CAP patient characteristics Smokers: S. pneumo, H. influenzae, Moraxella
Post viral bronchitis: S. pneumo
No co-morbidity: atypicals, viral
Alcoholic: S. pneumo, anaerobes
IV drug user: S. aureus
Airway obstruction: anaerobes
Animals: Psittacosis, Tularemia, Coxiella burnetii
3. Mechanisms of action of different antimicrobials Penicillins- Inhibits the transpeptidase enzyme step in peptidoglycan cell wall synthesis
1st generation:[ex Pen G] most streptococci, oral anaerobic coverage
2nd generation:[nafcillin] most streptococci, S. aureus (Penicillinase resistant)
3rd generation:[amoxicillin, ampicillin] most streptococci, basic G – coverage.
Amoxicillin is oral DOC for susceptible strains of S. pneumoniae
Amoxicillin with clavulanate treats beta lactamase producing bacteria like H. influenzae, Methicillin sensitive Staph aureus and anaerobes
4th generation:[piperacillin] extended spectrum, includes pseudomonas
Cephalosporins-inhibits cell wall synthesis
Parenteral DOC for CAP caused by susceptible strains of S pneumoniae, H influenzae, Staph aureus.
1st generation: G+ (including Staph aureus), basic G-
2nd generation: G+, diminished Staph aureus, improved G- coverage, some anaerobic coverage
3rd generation: further diminished S. aureus, further improved G-, some Pseudomonal coverage and diminished G+ coverage
4th generation: same as 3rd plus coverage against Pseudomonas
**note that neither group is effective against “atypicals”
4. Macroglides-inhibits 50s subunit of ribosome in protein synthesis
Treats mycoplasma, legionnaire’s, chlamydial infections
Active against most common pathogens and atypical agents. Macroglide resistance is emerging to Strep pneumoniae
Fluoroquinolones-inhibits DNA gyrase
Broad spectrum against likely agents of CAP. Active against penicillin resistant Strep pneumoniae. Resistance developing.
1st generation: G- NOT pseudomonas, UTI only, NO atypicals
2nd generation: G- including pseudomonas, S. aureus, some atypicals NOT pneumococcus
3rd generation: G-, G+, expanded atypicals
4th generation: same as 3rd plus enhanced coverage of pneumococcus, decreased activity vs pseudomonas.
Tetracyclines- inhibits 30s subunit of ribosome in protein synthesis
G+ and G-, aerobic & anaerobic bacteria, “atypicals”- mycoplasma, chlamydia and category A bioterrorism agents
5. Streptococcus pneumoniae (2/3 of CAP cases) Properties: G + diplococci “lancet shaped”, a hemolytic. #1 cause CAP: “rusty sputum”, single rigor, fever.
Tx and dose:
sensitive strains treat with penicillin G 250,000-400,000 units/kg/day IV divided q 4-6 or amoxicillin (oral) 1g PO tid.
intermediate resistance strains are susceptible to 2nd/3rd generation parenteral cephalosporins and respiratory fluoroquinolones
Cefotaxime 1-2g IM/IV q6-8 or ceftriaxone1-2 g IM/IV q24h.
Levofloxicin 500mgIV/po qd (others: alatrofox-, gati-, moxi-)
Prevention: capsular vaccines (prevnar, pneumovax)
6. H. influenzae
trimethoprim-sulfamethoxazole, Ampicillin IV, Amoxicillin po, azithro/clarithromycin, doxycycline
If severe, 3rd gen cephalosporin
Enteric gram negatives
Anaerobes: clindamycin or beta lactam/beta lactamase inhibitor
Sensitive strains: Nafcillin or oxacillin (penicillinase resistant abx)
Legionella- fluroquinolone or azithromycin
Mycoplasma- erythro, azithro, clarithromycin, or fluoroquinolone
Chlamydia pneumoniae- doxycycline, erythrocyclin or floroquinolones
7. Duration of therapy S pneumoniae: until afebrile for 3-5d
C pneumoniae:7-14 d
M pneumoniae: not well established.
Legionella: 10-21 d
S aureus, P aeruginosa, Klebsiella, anaerobes >3weeks